In the research and development of solid oxide fuel cells (SOFCs), all the major difficulties encountered are related to material development, i.e. in an effort to find suitable materials to be used in SOFC components, such as anode, cathode, or electrolyte. Presently, the most commonly used SOFC anode material is a two phase nickel and yttria stabilized zirconia (Ni/YSZ) cermet, and since the electrical conductivity of Ni/YSZ cermet is strongly depended on its nickel content in a manner that the resistance decreased as the Ni/YSZ ratio was increased and thus the performance of the resulting SOFC is enhanced. On the other hand, it is found that La(1-x)SrxMnO3 (LSM) is the most suitable cathode material today. Since the porosity up to a certain percent is necessary to transport oxygen gas to the interface region between the electrolyte and the LSM cathode and thus the electrical conductivity of LSM cathode is strongly depended on its porosity, the resistance increased as the porosity in LSM cathode was increased. Thus, in addition to the ion conductivity of an electrolyte used in SOFCs, the electric conductivities of the anode and the cathode also have profound effects on the cell performance.
Conventionally, the performance tests and failure diagnoses that are used for testing SOFCs are concerned with the measurement in overall cell performance and assessment in longitudinal impedance. However, in order to produce a SOFC that is commercially viable, the SOFC must be made in a size at least as large as 5 cm×5 cm, or even in a size of 10 cm×10 cm. For those large-size SOFC, the results obtained from the performance tests or the impedance assessments are generally average values relating to the whole SOFC, and it is difficult to characterize and to quantify the area where the electrochemistry takes place. However, such local characteristic differences can be an importance factor affecting the performance and durability of the SOFC.
Generally, in a fuel cell measurement, the impedance analysis for anode material and cathode material is processed at ambient temperature using a four-point probe fixture. However, such analysis can be problematic while being processed under high temperature. Moreover, for those conventional performance test, impedance analysis and durability test, the good or bad of a cell that is being tested is simply represented by an average value, according to that any minute regional differences in the cell that can affect the performance of the cell will not be detected.
The following is a list of conventional fuel cell measurement techniques, which includes:                (1) In an article disclosed in Electrochemistry Communications, volume 3, issue 11, November 2001, pages 628-632, by Brett et al., a method of performing high spatial and time-resolution, non-intrusive and dynamic current measurements along the length of a single flow channel in a solid polymer fuel cell is provided. In this article, it suggests that the farther in the flow channel that is to the inlet, the lower the current density will be, and along with the decreasing in the operation voltage, the larger the difference in the current density will be, resulting that the measurement of performance is unevenly distributed across the fuel cell. In addition, the aforesaid measurement is designed specifically for fuel cells with single flow channel that it is not suitable for measuring large-sized fuel cells.        (2) In an article disclosed in Solid State Ionics, volume 160 (2003), pages 15-26, by Jiang et. al., the effect of contact area between electrode and current collector on the performance of anode-supported solid oxide fuel cells (SOFC) has been investigated using current collector with various contact area on the PSM cathode side. Nevertheless, the aforesaid measurement can not be adapted for testing the overall performance of the SOFC, and also it is difficult to characterize and to quantify the area where the electrochemistry takes place for obtaining local characteristic differences in the SOFC.        (3) In an article disclosed in Solid State Ionics, volume 177 (2006), pages 2045-2051, by Metzger et. al., a new measurement system is provided for determining local effects and identifying critical parameters in a fuel cell. For technical applications, the fuel cell is divided and integrated in a metallic housing while allowing a process for determining the voltage distribution all over the fuel call to be performed upon the working fuel cell. In addition to the fuel cell had to be divided and segmented before the measurement can be performed, the aforesaid system is not capable of measuring anode impedance and cathode impedance.        (4) In an article disclosed in Renewably Energy, volume 33 (2008), pages 2580-2588, by Chiang et. al., the main objective is to evaluate the fuel/oxidant gas distributions as well as thermal stresses of an anode-supported solid oxide fuel cell (SOFC) test cell under different operating conditions. In this study, the commercial computational fluid dynamics (CFD) code Star-CD with es-sofc module is employed to simulate the current-voltage (I-V) characteristics and to provide the temperature field of the cell to the commercial code MARC for further thermal stress analysis. The simulation results indicate that the cells experience higher principal stresses at lower cell voltages due to a higher local current density and a higher temperature gradient. The result of a digital analysis provided in the paper is obtained under a homogeneous assumption, but if there are local characteristic differences in the SOFC, the result should be calibrated according to actual experiment.        
Moreover, there are already many studies relating to fuel cell measurement. One of which is a tool for testing fuel cells disclosed in TW Pat. No. M272988. The tool for testing fuel cells comprises: a top platform; a bottom platform; a top mold, mounted on the top platform; a bottom mold, being formed with an accommodation space to be used for receiving a fuel cell module that is to be test and being mounted on the bottom platform while allowing the bottom mold to be spaced from the top mold by a stroke distance; and a plurality of drivers, each being configured with a drive shaft and each being fixedly mounted on the bottom platform; wherein the drive shafts of the plural drivers are fixedly secured to the top platform while allowing the axes thereof to be parallel with one another; and each drive shaft is configured for allowing each to be moved by a distance exactly equal to the stroke distance. Operationally, when the drive shafts of the plural drivers are moved by the stroke distance, the top mold and the bottom mold will be moved accordingly to engage tightly with each other while enabling the fuel cell module to be sandwiched between the top mold and the bottom mold so as to be tested. Nevertheless, while using the aforesaid tool for testing fuel cells, the fuel cell is generally being integrated with other components, such as current-collector layer, splitter plate or end panel, etc., into a single cell module that can only be test as a whole and thus is unable to obtain local characteristic differences in the single cell module.
Another such study is a rapid set-up, double chamber detecting device of SOFC positive electrolyte negative (PEN) assembly, that is disclosed in TW Pat. Pub. No. 201015770. The double chamber detecting device comprises: a metal case, insulated ceramic rings, an easily install chamber of anode, and the current collected unit of anode and cathode. This device is able to measure the performance of SOFC PEN plate rapidly and repeatedly, it's costless, easy to assemble, rapid set-up, high safety, excellent sealing and etc. In addition, it is helpful to develop the commercial application of SOFC PEN plate and improve the material study of SOFC PEN. However, since such detecting device is generally made of metal that can be easily oxidized under high temperature causing by the operating fuel cell, the impedance of the fuel cell that is being tested is increased. In addition, as the resulting oxide might peel off from the surface of the metal detecting device after being used repetitively for a long period of time, not only the geometry of the detecting device might changed accordingly, but also the poisoning effect resulting from the ionization of the peeled oxide can cause the degradation of the fuel cell to accelerate, and therefore, adversely affecting the measurement of SOFC performance.
Another such study is a method for fabricating an array of electrode and electrolyte materials for use in solid oxide fuel cells, which is disclosed in U.S. Pat. No. 7,910,158. The aforesaid patent includes systems and methods for synthesizing and optimizing the performance of electrodes and electrode-electrolyte combinations and utilizes small-scale techniques to perform such optimization based on chemical composition and variable processing. Advantageously, rapid device performance systems and methods coupled with structural and surface systems and methods allow for an increased discovery rate of new materials for solid oxide fuel cells. However, it is unable to test any of the commercial fuel cells longitudinally, laterally or locally.
Another such study is an electrical current measurement in a fuel cell, which is disclosed in U.S. Pat. Pub. No. 20050260471. Operationally, a plurality of electrical current sensors for a set of fuel cell stacks in series independently measure electrical current in a fuel cell, and an acceptability status is determined for each electrical current sensor by independent comparison of each sensor measurement to the individual values of the other sensor measurements. A characteristic current measurement is derived from all electrical current sensors having an acceptability status that is trustworthy. However, it is not designed for and incapable of obtaining local characteristic differences in a single fuel cell.
Therefore, it is in need of a testing device for solid oxide fuel cell for overcoming the aforesaid shortcomings.